First the flood... now the rats??

By

HLN Staff

Updated 12:42 PM EDT,

Fri November 2, 2012

New Yorkers have enough to worry about above ground. But below, the city's massive rat population may be on the move after Sandy, adding another potential concern to residents' long list of post-superstorm challenges.

But for all we hear about New York's legendary sewer-dwelling armies of rodents, is this really likely to happen? Millions of rats flushed from their subterranean habitat?

Dr. Rick Ostfeld is a senior scientist who specializes in both disease ecology and rodent population dynamics at New York's Cary Institute of Ecosystem Studies. We asked him about the potential for a rat infestation and where these rats may go next if they've been flooded from their homes.

HLN: Do you think this will actually happen? A broad dispersal of the rat population?

Dr. Rick Ostfeld: I think it’s quite likely that rat populations that inhabited low-lying areas of NYC (sewers, storm drains, subways, etc.) will be massively affected by Sandy. Some individuals likely will be killed, but rats are excellent swimmers and climbers, and I expect them to disperse widely over the next few days to weeks. Some might return home when the floodwaters subside, but others will set up shop in some new place.

HLN: Is it possible to know how many rats may be living around NYC? Best guess?

Ostfeld: No one has done the type of study needed to make a good estimate -- this would involve capturing, marking, and recapturing rats all over the city, a rather tall order. But my understanding is that there are at least as many rats as there are people in NYC.

HLN: Where will these rats try to go?

Ostfeld: Initially to higher ground. Unfortunately, much of that higher ground consists of stores, apartments, warehouses, schools, and other places where we don’t want rat companions. We can expect a phase of dispersing, wandering rats followed by their establishing new colonies and social orders. The wandering phase, which could take weeks, presents a problem as the animals mix with one another (increasing risk of disease transmission to other rats) and look for food, often near people.

HLN: Many people will cringe when thinking about this problem. But beyond the "ick" factor, what are the potential health risks and likelihood of any kind of outbreak?

Ostfeld: Rats can carry a number of pathogens that are dangerous to people, including leptospirosis, typhus, salmonella, and hantaviruses. Rats were the source of the flea-borne plague bacteria that decimated Europe in the Middle Ages. Rats often transmit these pathogens among themselves but don’t get sick or die because they develop partial immunity. But when infected rats disperse and mingle with susceptible rats elsewhere in the city, we might expect outbreaks in new rat populations, which could spill over into people. So, we should be aware of this possibility and be ready to control new rat infestations and also to seek medical attention if rat-borne disease is suspected.

HLN: Have rats been "flushed out" in NYC before in large numbers?

Ostfeld: Not that I’m aware of. There’s an interesting PBS special called "Rat Attack" that describes rat “plagues” that occur after bamboo flowering causes outbreaks and massive dispersal. Not the same thing, but some lessons there.